Photovoltaic device

ABSTRACT

A large surface area photovoltaic device having high conversion efficiency and excellent mass productivity is provided. A photovoltaic device  100  having a photovoltaic layer  3  comprising a crystalline silicon layer formed on a substrate  1 , wherein the crystalline silicon layer has a crystalline silicon i-layer  42 , and the crystalline silicon i-layer  42  has a substrate in-plane distribution represented by an average value for the Raman peak ratio, which represents the ratio of the Raman peak intensity for the crystalline silicon phase relative to the Raman peak intensity for the amorphous silicon phase, that is not less than 4 and not more than 8, a standard deviation for the Raman peak ratio that is not less than 1 and not more than 3, and a proportion of regions in which the Raman peak ratio is not more than 4 of not less than 0% and not more than 15%.

TECHNICAL FIELD

The present invention relates to a photovoltaic device, and relatesparticularly to a photovoltaic device in which the electric powergeneration layer is formed by deposition.

BACKGROUND ART

One known example of a photovoltaic device used in a solar cell thatconverts the energy from sunlight into electrical energy is a thin-filmsilicon-based photovoltaic device comprising a photovoltaic layer formedby using a plasma enhanced CVD method or the like to deposit thin filmsof a p-type silicon-based semiconductor (p-layer), an i-typesilicon-based semiconductor (i-layer) and an n-type silicon-basedsemiconductor (n-layer).

Advantages of thin-film silicon-based solar cells include thecomparative ease with which the surface area can be increased, and thefact that the film thickness is approximately 1/100th that of acrystalline solar cell, meaning minimal material is required. As aresult, thin-film silicon-based solar cells can be produced at lowercost than crystalline solar cells. However, drawbacks of thin-filmsilicon-based solar cells include lower conversion efficiency than thatof crystalline solar cells, and a slow deposition rate, resulting inpoor productivity.

A tandem-type silicon-based solar cell in which a photovoltaic layercomprising an i-layer composed of amorphous silicon and a photovoltaiclayer comprising an i-layer composed of crystalline silicon are stackedtogether is effective in improving the conversion efficiency of athin-film silicon-based solar cell. The crystallinity of the crystallinesilicon i-layer and the conversion efficiency of the solar cell areclosely correlated, and it is known that the highest conversionefficiency is achieved when the crystalline silicon i-layer exhibitscrystallinity that is close to the boundary between amorphism andcrystallinity.

The crystallinity of the crystalline silicon i-layer is dependent uponthe film deposition conditions such as the substrate temperature duringdeposition and the hydrogen dilution ratio. The crystallinity isrepresented, for example, by the ratio 1c/1a in the Raman spectrumbetween the crystalline silicon peak intensity at 520 cm⁻¹ and theamorphous silicon peak intensity at 480 cm⁻¹. Patent citation 1discloses a process for producing a solar cell having high conversionefficiency by depositing the crystalline silicon i-layer underconditions where the substrate temperature Tsub and the ratio 1c/1asatisfy the relational formula 700≦Tsub×1c/1a≦1600.

One technique for improving the mass productivity of solar cellsinvolves forming a crystalline silicon i-layer of uniform crystallinityand thickness to maintain solar cell performance, while increasing thedeposition rate. Further, in another technique, a solar cell module isproduced using a large surface area substrate. Generally, in theproduction of large surface area modules using a plasma enhanced CVDmethod, the crystallinity and film thickness of the crystalline siliconi-layer tend to exhibit distributions within the substrate plane thatcorrespond with the gas flow and the discharge distribution. On theother hand, in order to improve the mass productivity of the solar cell,a larger RF power must be supplied to the plasma electrode to increasethe deposition rate of the crystalline silicon i-layer. However, thisalso increases the plasma discharge distribution within the substrateplane, causing a broadening of the crystallinity and film thicknessdistributions within the substrate plane. As a result, in the case of alarge surface area substrate, depositing the crystalline silicon i-layeruniformly across the substrate plane in order to achieve a level ofcrystallinity that yields superior performance for the solar cellcontaining the crystalline silicon i-layer is problematic, and achievinga combination of a high deposition rate and high performance isextremely difficult.

One technique for depositing a crystalline silicon layer of uniformcrystallinity and film thickness on a large surface area substrate hasbeen reported in non-patent citation 1, and comprises the deposition ofa crystalline silicon layer using a short-pulsed plasma CVD method. In ashort-pulsed CVD method, by pulsing an excited plasma, the spatialnon-uniformity of the applied electric field during the plasma ON phasesis moderated and the spatial distribution of the active species becomesmore uniform, leading to improvements in the uniformity of thecrystallinity and the film thickness. As a result, a large surface areasolar cell having high conversion efficiency can be realized.

Patent Citation 1: Publication of Japanese Patent No. 3,943,080.

Non Patent Citation 1: Y. Fujioka et al., “Large scale, high-efficiencythin-film silicon solar cells fabricated by short-pulsed plasma CVDmethod”, PVSEC14th (Bangkok, 2004 January).

DISCLOSURE OF INVENTION

In the short-pulsed plasma CVD method disclosed in non-patent citation1, uniform crystallinity and film thickness within the plane areachieved by pulsing of the plasma. However, despite the fact that theactive species are generated efficiently so that the deposition ratedoes not decrease as a result of the pulsing, the deposition rate isstill less than that obtained for deposition using a typical continuousplasma. In other words, conventionally there are no techniques availablethat combine rapid deposition with favorable crystallinity uniformityand film thickness uniformity.

Achieving uniform deposition of a crystalline silicon i-layer within thesubstrate plane so as to obtain a level of crystallinity that yieldssuperior performance, together with rapid deposition, thereby enablinglarge surface area solar cell modules comprising a crystalline siliconi-layer to be produced with a combination of superior solar cell massproductivity and superior performance is extremely difficult.Accordingly, in order to achieve both favorable mass productivity andfavorable performance for a solar cell, some variation in the in-planedistribution of the crystallinity of the crystalline silicon i-layermust be tolerated, and a permissible range must be set for the in-planedistribution of the crystallinity. It is known that if the crystallinityof the crystalline silicon i-layer is low, then the sensitivity of thelayer to light of longer wavelengths (such as wavelengths of 600 nm ormore) deteriorates, causing a decrease in the solar cell performance. Asa result, it has been thought that the permissible range for thein-plane distribution of the crystallinity within the crystallinesilicon i-layer must be set so as to exclude the existence of lowcrystallinity regions. Here, a “low crystallinity region” refers to aregion in which, for example, the ratio within the crystalline siliconlayer of the Raman peak intensity for the crystalline silicon phaserelative to the Raman peak intensity for the amorphous silicon phase isnot more than approximately 3 or 4.

The present invention has been developed in light of the abovecircumstances, and has an object of providing a large surface areaphotovoltaic device having high conversion efficiency and excellent massproductivity.

In order to achieve the above object, the present invention provides aphotovoltaic device having a photovoltaic layer comprising a crystallinesilicon layer formed on a substrate, wherein the crystalline siliconlayer has a crystalline silicon i-layer, and the crystalline siliconi-layer has a substrate in-plane distribution represented by an averagevalue for the Raman peak ratio, which represents the ratio of the Ramanpeak intensity for the crystalline silicon phase relative to the Ramanpeak intensity for the amorphous silicon phase, that is not less than 4and not more than 8, a standard deviation for the Raman peak ratio thatis not less than 1 and not more than 3, and a proportion of regions inwhich the Raman peak ratio is not more than 4 of not less than 0% andnot more than 15%. The Raman peak ratio is represented by the ratio1c/1a, within a Raman spectrum measured using laser light having awavelength of 532 nm, of the peak intensity 1c for the crystallinesilicon phase at 520 cm⁻¹ relative to the peak intensity 1a for theamorphous silicon phase at 480 cm⁻¹.

In order to obtain a photovoltaic device having high conversionefficiency, there is an ideal range for the Raman peak ratio for thecrystalline silicon i-layer, and if the Raman peak ratio is too low,then the sensitivity of the i-layer to longer wavelength light having awavelength 700 nm or longer decreases, resulting in reduced conversionefficiency. However, it was discovered that if regions having a lowRaman peak ratio of not more than 4 existed within the substrate plane,then the conversion efficiency actually increased. However, if theproportion of these regions having a Raman peak ratio or not more than 4exceeds 15%, then not only does the conversion efficiency decrease, butpeeling may occur as a result of the stress generated within thesubstrate plane between the regions having a low Raman peak ratio andthe regions having a high Raman peak ratio, which is problematic interms of long-term stability. A photovoltaic device in which the Ramanpeak ratio of the crystalline silicon i-layer has a substrate in-planedistribution represented by the distribution described above is ahigh-output photovoltaic device.

Moreover, the present invention also provides a photovoltaic devicehaving a photovoltaic layer comprising a crystalline silicon layerformed on a substrate, wherein the crystalline silicon layer has acrystalline silicon i-layer, the size of the surface of the substrate onwhich the photovoltaic layer is formed is at least 1 m square, and thecrystalline silicon i-layer has a substrate in-plane distributionrepresented by an average value for the Raman peak ratio, whichrepresents the ratio of the Raman peak intensity for the crystallinesilicon phase relative to the Raman peak intensity for the amorphoussilicon phase, that is not less than 5 and not more than 8, a standarddeviation for the Raman peak ratio that is not less than 1 and not morethan 3, and a proportion of regions in which the Raman peak ratio is notmore than 4 of not less than 0% and not more than 10%.

In those cases where the surface of the substrate on which thephotovoltaic layer is formed is at least 1 m square, if the proportionof those regions having a Raman peak ratio of not more than 4 exceeds10%, then the probability of regions of low Raman peak ratio beingconcentrated within a localized area increases, which can lead toproblems such as a tendency for the output of the photovoltaic device todecrease, and an increased chance that peeling may occur within thecrystalline silicon layer. In a large surface area photovoltaic device,by ensuring that the Raman peak ratio for the crystalline siliconi-layer has a substrate in-plane distribution represented by thedistribution described above, a high-output photovoltaic device can beobtained.

In the present invention, the crystalline silicon i-layer is preferablydeposited at a deposition rate of not less than 1.5 nm/sec. Generally,if a crystalline silicon layer is deposited rapidly, then the substratein-plane distributions for the crystallinity and the film thickness tendto increase. In contrast, with the photovoltaic device of the presentinvention, even if the crystalline silicon i-layer is deposited at arapid rate of not less than 1.5 nm/sec, because the crystalline siliconi-layer has a Raman peak ratio within the substrate plane that satisfiesthe substrate in-plane distribution described above, a high-outputphotovoltaic device can be obtained with a high degree of productivity.Ensuring favorable productivity for solar cell modules at a depositionrate lower than 1.5 nm/sec would require the installation of a pluralityof parallel crystalline silicon i-layer deposition chambers, but thissimply leads to dramatic and undesirable increases in plant equipmentcosts.

In the present invention, the photovoltaic layer may further comprise anamorphous silicon layer, wherein the film thickness of the amorphoussilicon i-layer within this amorphous silicon layer is not less than 170nm and not more than 250 nm.

By setting the film thickness of the amorphous silicon i-layer to avalue within the above range, light-induced degradation of thephotovoltaic device can be suppressed, and a high stabilized output canbe achieved.

In such cases, an intermediate contact layer is preferably providedbetween the crystalline silicon layer and the amorphous silicon layer.Short wavelength light that is transmitted through the amorphous siliconlayer without being completely absorbed is reflected by the intermediatecontact layer, thereby lengthening the light path within the amorphoussilicon layer and enabling more efficient absorption of the shortwavelength light. Further, the intermediate contact layer also improvesthe contact properties between the crystalline silicon layer and theamorphous silicon layer. As a result, the generated electrical currentcan be increased without increasing the film thickness of the amorphoussilicon layer, meaning a photovoltaic device of high conversionefficiency can be obtained.

According to the present invention, by ensuring that the Raman peakratio of the crystalline silicon i-layer has a substrate in-planedistribution described above, a photovoltaic device having highconversion efficiency can be obtained even when the crystalline siliconlayer is deposited on a large surface area substrate at a rapiddeposition rate in order to improve the productivity.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A cross-sectional view schematically illustrating the structureof a photovoltaic device according to an embodiment of the presentinvention.

FIG. 2 A schematic illustration describing an embodiment for producing asolar cell panel that represents a photovoltaic device according to thepresent invention.

FIG. 3 A schematic illustration describing an embodiment for producing asolar cell panel that represents a photovoltaic device according to thepresent invention.

FIG. 4 A schematic illustration describing an embodiment for producing asolar cell panel that represents a photovoltaic device according to thepresent invention.

FIG. 5 A schematic illustration describing an embodiment for producing asolar cell panel that represents a photovoltaic device according to thepresent invention.

FIG. 6 A graph illustrating the relationship between the Raman peakratio for the crystalline silicon i-layer and the photovoltaicconversion efficiency in a tandem-type solar cell.

FIG. 7 A graph illustrating the relationship between the average valuefor the Raman peak ratio for the crystalline silicon i-layer and themodule output in a tandem-type solar cell module having a substrate sizeof 1.4 m×1.1 m.

FIG. 8 A graph illustrating the relationship between the proportion ofregions within the crystalline silicon i-layer having a Raman peak ratioof not more than 4 and the module output in a tandem-type solar cellmodule having a substrate size of 1.4 m×1.1 m.

FIG. 9 A graph illustrating the relationship between the average valuefor the Raman peak ratio for the crystalline silicon i-layer and themodule output in a tandem-type solar cell module having a substrate sizeof 0.7 m×1.1 m.

FIG. 10 A graph illustrating the relationship between the proportion ofregions within the crystalline silicon i-layer having a Raman peak ratioof not more than 4 and the module output in a tandem-type solar cellmodule having a substrate size of 0.7 m×1.1 m.

Explanation of Reference:   1: Substrate   2: Transparent electrodelayer   3: Photovoltaic layer   4: Back electrode layer   5:Intermediate contact layer   6: Solar cell module  31: Amorphous siliconp-layer  32: Amorphous silicon i-layer  33: Amorphous silicon n-layer 41: Crystalline silicon p-layer  42: Crystalline silicon i-layer  43:Crystalline silicon n-layer  91: First cell layer  92: Second cell layer100: Photovoltaic device

BEST MODE FOR CARRYING OUT THE INVENTION

A description of an embodiment of a photovoltaic device according to thepresent invention is presented below.

FIG. 1 is a schematic illustration of the structure of a photovoltaicdevice according to this embodiment. A photovoltaic device 100 is asilicon-based solar cell, and comprises a substrate 1, a transparentelectrode layer 2, a first cell layer 91 (an amorphous silicon series)and a second cell layer 92 (a crystalline silicon series) that functionas a photovoltaic layer 3, and a back electrode layer 4. Here, the terms“silicon-based” and “silicon series” are generic terms that includesilicon (Si), silicon carbide (SiC) and silicon germanium (SiGe).Further, a crystalline silicon series describes a silicon series otherthan an amorphous silicon series, and includes both microcrystallinesilicon series and polycrystalline silicon series.

A description of the steps for producing a photovoltaic device accordingto the present embodiment is presented below, using a solar cell panelas an example, with reference to FIG. 2 through FIG. 5.

(1) FIG. 2( a)

A soda float glass substrate (for example, a large surface areasubstrate of 1.4 m×1.1 m×thickness: 3 to 6 mm, where the length of oneside exceeds 1 m) is used as the substrate 1. The edges of the substrateare preferably subjected to corner chamfering or R-face chamfering toprevent damage caused by thermal stress or impacts or the like.

(2) FIG. 2( b)

A transparent electrode film comprising mainly tin oxide (SnO₂) andhaving a film thickness of approximately not less than 500 nm and notmore than 800 nm is deposited as the transparent electrode layer 2,using a thermal CVD apparatus at a temperature of approximately 500° C.During this deposition, a texture comprising suitable unevenness isformed on the surface of the transparent electrode film. In addition tothe transparent electrode film, the transparent electrode layer 2 mayinclude an alkali barrier film (not shown in the figure) formed betweenthe substrate 1 and the transparent electrode film. The alkali barrierfilm is formed using a thermal CVD apparatus at a temperature ofapproximately 500° C. to deposit a silicon oxide film (SiO₂) having afilm thickness of not less than 50 nm and not more than 150 nm.

(3) FIG. 2( c)

Subsequently, the substrate 1 is mounted on an X-Y table, and the firstharmonic of a YAG laser (1064 nm) is irradiated onto the surface of thetransparent electrode layer, as shown by the arrow in the figure. Thelaser power is adjusted to ensure an appropriate process speed, and thetransparent electrode film is then moved in a direction perpendicular tothe direction of the series connection of the electric power generationcells, thereby causing a relative movement between the substrate 1 andthe laser light, and conducting laser etching across a strip having apredetermined width of approximately 6 mm to 15 mm to form a slot 10.

(4) FIG. 2( d)

Using a plasma enhanced CVD apparatus, a p-layer, an i-layer and ann-layer, each composed of a thin film of amorphous silicon, aredeposited as the first cell layer 91. Using SiH₄ gas and H₂ gas as themain raw materials, and under conditions including a reduced pressureatmosphere of not less than 30 Pa and not more than 1,000 Pa and asubstrate temperature of approximately 200° C., an amorphous siliconp-layer 31, an amorphous silicon i-layer 32 and an amorphous siliconn-layer 33 are deposited, in this order, on the transparent electrodelayer 2, with the p-layer closest to the surface from which incidentsunlight enters. The amorphous silicon p-layer 31 is an amorphousB-doped silicon film having a film thickness of not less than 10 nm andnot more than 30 nm. The amorphous silicon i-layer 32 has a filmthickness of not less than 170 nm and not more than 250 nm. Theamorphous silicon n-layer 33 is a P-doped amorphous silicon film havinga film thickness of not less than 30 nm and not more than 50 nm. Acrystalline silicon n-layer composed of a P-doped crystalline siliconfilm may be provided instead of the amorphous silicon n-layer. A bufferlayer may be provided between the amorphous silicon p-layer 31 and theamorphous silicon i-layer 32 in order to improve the interfaceproperties.

Using a plasma enhanced CVD apparatus, a p-layer, an i-layer and ann-layer, each composed of a thin film of crystalline silicon, aredeposited as the second cell layer 92 on top of the first cell layer 91.Using SiH₄ gas and H₂ gas as the main raw materials, and underconditions including a reduced pressure atmosphere of not more than3,000 Pa, a substrate temperature of approximately 200° C. and a plasmageneration frequency of not less than 40 MHz and not more than 100 MHz,a crystalline silicon p-layer 41, a crystalline silicon i-layer 42 and acrystalline silicon n-layer 43 are deposited in this order.

In the present embodiment, the crystalline silicon p-layer 41 is aB-doped crystalline silicon film having a film thickness of not lessthan 10 nm and not more than 50 nm. The crystalline silicon i-layer 42has a film thickness of not less than 1.2 μm and not more than 3.0 μm.The crystalline silicon n-layer 43 is a P-doped crystalline silicon filmhaving a film thickness of not less than 20 nm and not more than 50 nm.

FIG. 6 illustrates the relationship between the Raman peak ratio for thecrystalline silicon i-layer and the photovoltaic conversion efficiencyin a tandem-type solar cell. In this figure, the horizontal axisrepresents the Raman peak ratio 1c/1a for the crystalline siliconi-layer, and the vertical axis represents the conversion efficiency (thenormalized value) of the tandem-type solar cell. It is evident that whenthe Raman peak ratio for the crystalline silicon i-layer falls below 4,the photovoltaic conversion efficiency of the cell decreases rapidly.Based on the results of FIG. 6, it could be thought that in a solar cellmodule using a large surface area substrate, it should be preferable toensure that the Raman peak ratio for the crystalline silicon i-layeracross the entire substrate is set to a value within the range thatyields high conversion efficiency for an individual cell. However, incontrast, by ensuring that a predetermined quantity of regions having aRaman peak ratio of 4 or less exist within the substrate plane, theconversion efficiency of the solar cell module can actually beincreased.

The Raman peak ratio distribution for the crystalline silicon i-layercan be controlled via the deposition conditions, such as the level ofelectric power applied to the plasma electrode during deposition and thehydrogen dilution ratio H₂/SiH₄. The Raman peak ratio distribution forthe crystalline silicon i-layer within the substrate plane is controlledso that the average value of the Raman peak ratio is not less than 4 andnot more than 8, the standard deviation is not less than 1 and not morethan 3, and the proportion of regions for which the Raman peak ratio isnot more than 4 is not less than 0% and not more than 15%, andpreferably not less than 2% and not more than 6%. Particularly in thosecases where, as in the present embodiment, a large surface areasubstrate having a size exceeding 1 m square is used, the probability ofregions of low Raman peak ratio being concentrated within a localizedarea increases, and therefore it is desirable that the proportion ofregions for which the Raman peak ratio is not more than 4 is suppressedto a value within a predetermined range. Namely, the Raman peak ratiodistribution for the crystalline silicon i-layer within the substrateplane is controlled so that the average value of the Raman peak ratio isnot less than 5 and not more than 8, the standard deviation is not lessthan 1 and not more than 3, and the proportion of regions for which theRaman peak ratio is not more than 4 is not less than 0% and not morethan 10%, preferably not less than 1% and not more than 7%, and morepreferably not less than 2% and not more than 6%.

Because the crystalline silicon i-layer 42 is thicker than the otherlayers, the deposition rate for the crystalline silicon i-layer is ratecontrolling for the productivity of the solar cell module. In order toincrease the productivity, the crystalline silicon i-layer 42 is formedat a deposition rate of at least 1.5 nm/sec, and preferably 2.0 nm/secor higher.

In the present embodiment, by ensuring that the thickness of theamorphous silicon i-layer 32 is not less than 170 nm and not more than250 nm, light-induced degradation of the solar cell can be prevented. Ina tandem-type solar cell where an amorphous silicon layer and acrystalline silicon layer are stacked as the photovoltaic layer, thelight-induced degradation rate can be suppressed to 10% or less. As aresult, the stabilized output can be improved for those situations wherethe solar cell is used over an extended period exceeding 1,000 hours.

An intermediate contact layer 5 that functions as a semi-reflective filmfor improving the contact properties between the first cell layer 91 andthe second cell layer 92 and achieving electrical current consistencymay be provided on the first cell layer 91. For example, a GZO (Ga-dopedZnO) film with a film thickness of not less than 20 nm and not more than100 nm may be formed as the intermediate contact layer 5 using a DCsputtering apparatus with a Ga-doped ZnO sintered body as the target.

(5) FIG. 2( e)

The substrate 1 is mounted on an X-Y table, and the second harmonic of alaser diode excited YAG laser (532 nm) is irradiated onto the filmsurface of the photovoltaic layer 3, as shown by the arrow in thefigure. With the pulse oscillation set to not less than 10 kHz and notmore than 20 kHz, the laser power is adjusted so as to achieve asuitable process speed, and laser etching is conducted at a pointapproximately 100 μm to 150 μm to the side of the laser etching linewithin the transparent electrode layer 2, so as to form a slot 11. Thelaser may also be irradiated from the side of the substrate 1. In thiscase, because the high vapor pressure generated by the energy absorbedby the first cell layer 91 of the photovoltaic layer 3 can be utilized,more stable laser etching processing can be performed. The position ofthe laser etching line is determined with due consideration ofpositioning tolerances, so as not to overlap with the previously formedetching line.

Using a sputtering apparatus, an Ag film and a Ti film are depositedsequentially as the back electrode layer 4 under a reduced pressureatmosphere and at a temperature of approximately 150° C. In thisembodiment, the back electrode layer 4 is formed by sequentiallystacking an Ag film having a thickness of not less than 200 nm and notmore than 500 nm, and a highly corrosion-resistant Ti film having athickness of not less than 10 nm and not more than 20 nm which acts as aprotective film. In order to reduce the contact resistance between then-layer of the second cell layer 92 and the back electrode layer 4 andimprove the reflectance, a GZO (Ga-doped ZnO) film with a film thicknessof not less than 50 nm and not more than 100 nm may be deposited betweenthe photovoltaic layer 3 and the back electrode layer 4 using asputtering apparatus. Furthermore, an Al film of not less than 250 nmand not more than 350 nm may be used instead of the Ti film. By using Alinstead of Ti, the material costs can be reduced while maintaining theanticorrosion effect.

(7) FIG. 3( b)

The substrate 1 is mounted on an X-Y table, and the second harmonic of alaser diode excited YAG laser (532 nm) is irradiated onto the substrate1, as shown by the arrow in the figure. The laser light is absorbed bythe photovoltaic layer 3, and by utilizing the high gas vapor pressuregenerated at this point, the back electrode layer 4 is removed byexplosive fracture. With the pulse oscillation set to not less than 1kHz and not more than 10 kHz, the laser power is adjusted so as toachieve a suitable process speed, and laser etching is conducted at apoint approximately 250 μm to 400 μm to the side of the laser etchingline within the transparent electrode layer 2, so as to form a slot 12.

(8) FIG. 3( c)

The electric power generation region is then compartmentalized, by usinglaser etching to remove the effect wherein the serially connectedportions at the film edges near the edges of the substrate are prone toshort circuits. The substrate 1 is mounted on an X-Y table, and thesecond harmonic of a laser diode excited YAG laser (532 nm) isirradiated onto the substrate 1. The laser light is absorbed by thetransparent electrode layer 2 and the photovoltaic layer 3, and byutilizing the high gas vapor pressure generated at this point, the backelectrode layer 4 is removed by explosive fracture, and the backelectrode layer 4, the photovoltaic layer 3 and the transparentelectrode layer 2 are removed. With the pulse oscillation set to notless than 1 kHz and not more than 10 kHz, the laser power is adjusted soas to achieve a suitable process speed, and laser etching is conductedat a point approximately 5 mm to 20 mm from the edge of the substrate 1,so as to form an X-direction insulation slot 15 as illustrated in FIG.3( c). A Y-direction insulation slot need not be provided at this point,because a film surface polishing and removal treatment is conducted onthe peripheral regions of the substrate 1 in a later step.

Completing the etching of the insulation slot 15 at a position 5 to 10mm from the edge of the substrate 1 is preferred, as it ensures that theinsulation slot 15 is effective in inhibiting external moisture fromentering the interior of the solar cell module 6 via the edges of thesolar cell panel.

Although the laser light used in the steps until this point has beenspecified as YAG laser light, light from a YVO4 laser or fiber laser orthe like may also be used in a similar manner.

(9) FIG. 4( a)

In order to ensure favorable adhesion and sealing of a backing sheet 24via EVA or the like in a subsequent step, the stacked films around theperiphery of the substrate 1 (in a peripheral region 14) are removed, asthey tend to be uneven and prone to peeling. Grinding or blast polishingor the like is used to remove the back electrode layer 4, thephotovoltaic layer 3, and the transparent electrode layer 2 from aregion that is 5 mm to 20 mm from the edge around the entire peripheryof the substrate 1, is closer to the substrate edge than the insulationslot 15 provided in the above step of FIG. 3( c) in the X direction, andis closer to the substrate edge than the slot 10 near the substrate edgein the Y direction. Grinding debris or abrasive grains are removed bywashing the substrate 1.

(10) FIG. 4( b)

A terminal box attachment portion is prepared by providing an openthrough-window in the backing sheet 24 and exposing a collecting plate.A plurality of layers of an insulating material are provided in thisopen through-window portion in order to prevent external moisture andthe like entering the solar cell module.

Processing is conducted so as to enable current collection, using acopper foil, from the series-connected solar cell electric powergeneration cell at one end, and the solar cell electric power generationcell at the other end, in order to enable electric power to be extractedfrom a terminal box portion on the rear surface of the solar cell panel.In order to prevent short circuits between the copper foil and thevarious portions, an insulating sheet that is wider than the width ofthe copper foil is provided.

Following arrangement of the collecting copper foil and the like atpredetermined positions, the entire solar cell module 6 is covered witha sheet of an adhesive filling material such as EVA (ethylene-vinylacetate copolymer) arranged so as not to protrude beyond the substrate1.

A backing sheet 24 with a superior waterproofing effect is positioned ontop of the EVA. In this embodiment, in order to achieve a superiorwaterproofing and moisture-proofing effect, the backing sheet 24 isformed as a three-layer structure comprising a PET sheet, an Al foil,and a PET sheet.

The structure comprising the components up to and including the backingsheet 24 arranged in predetermined positions is subjected to internaldegassing under a reduced pressure atmosphere and under pressing atapproximately 150° C. to 160° C. using a laminator, thereby causingcross-linking of the EVA that tightly seals the structure.

(11) FIG. 5( a)

A terminal box 23 is attached to the back of the solar cell module 6using an adhesive.

(12) FIG. 5( b)

The copper foil and an output cable from the terminal box 23 areconnected using solder or the like, and the interior of the terminal boxis filled and sealed with a sealant (a potting material). This completesthe production of the solar cell panel 50.

(13) FIG. 5( c)

The solar cell panel 50 formed via the steps up to and including FIG. 5(b) is then subjected to an electric power generation test, as well asother tests for evaluating specific performance factors. The electricpower generation test is conducted using a solar simulator that emits astandard sunlight of AM 1.5 (1,000 W/m²).

(14) FIG. 5( d)

In tandem with the electric power generation test (FIG. 5( c)), avariety of specific performance factors including the externalappearance are evaluated.

EXAMPLES Example 1

Using a CVD method, an amorphous silicon layer and a crystalline siliconlayer were formed, as the first cell layer 91 and the second cell layer92 respectively, on a glass substrate of dimensions 1.4 m×1.1 m, thusforming a tandem-type solar cell module. Deposition of the crystallinesilicon i-layer 42 was conducted at a deposition rate of 2 nm/sec, andthe electric power applied to the plasma electrode and the hydrogendilution ratio were adjusted appropriately to control the distributionof the Raman peak ratio within the substrate plane.

Following measurement of the solar cell module output, the substrate waspartitioned. Samples were taken from 24 locations within the substrateplane, and following removal of the back electrode layer 4 from eachsample by wet etching using hydrogen peroxide (concentration: 30%) anddilute hydrochloric acid (molar concentration: 0.2), the Raman spectrumwas measured with the crystalline silicon n-layer 43 exposed at thesurface, and the Raman peak ratio 1c/1a was determined.

The output of the produced solar cell module, the distribution range,average value, and standard deviation for the Raman peak ratio for thecrystalline silicon i-layer, and the proportion of regions having aRaman peak ratio of not more than 4 are shown in Table 1. The standarddeviation was not less than 1 and not more than 3 for all of thesamples. The film thickness distribution for the crystalline siliconi-layer was within a range from ±15 to 25% relative to the average filmthickness.

TABLE 1 Proportion of regions having Raman Module Raman peak AverageStandard peak ratio of not output ratio range value deviation more than4 (%) (W) 5~10 7.5 1.1 0 145 3~11 6.5 2.2 2 158 3~10 6.3 1.7 3 160 1~105.2 2.4 6 150 3~9 5.8 1.4 9 145 3~10 5.8 1.7 16 140 2~9 5.5 1.9 31 1102~8 4.8 1.7 38 100 2~7 3.8 1.4 58 80

FIG. 7 illustrates the relationship between the average value for theRaman peak ratio for the crystalline silicon i-layer and the solar cellmodule output in a solar cell module having a substrate size of 1.4m×1.1 m. In this figure, the horizontal axis represents the averagevalue for the Raman peak ratio, and the vertical axis represents themodule output. A high output was obtained for those solar cell moduleshaving an average value of not less than 5 and not more than 8. FIG. 8illustrates the relationship between the proportion of regions withinthe crystalline silicon i-layer having a Raman peak ratio of not morethan 4 and the module output in a tandem-type solar cell module having asubstrate size of 1.4 m×1.1 m. In this figure, the horizontal axisrepresents the proportion of regions having a Raman peak ratio of notmore than 4, and the vertical axis represents the module output. A highoutput was obtained for proportions of 10% or less. In contrast, oncethis proportion exceeded 10%, the output exhibited a declining trend.Further, peeling of the crystalline silicon layer was observed withinsome modules.

As described above, the initial output for a solar cell module having acrystalline silicon i-layer for which the Raman peak ratio within thesubstrate plane had an average value of not less than 5 and not morethan 8 and a standard deviation of not less than 1 and not more than 3,and for which the proportion of regions having a Raman peak ratio of notmore than 4 was not more than 10%, was a high output equivalent to atleast 90% of the maximum initial output (160 W).

Example 2

Using a CVD method, an amorphous silicon layer and a crystalline siliconlayer were formed, as the first cell layer 91 and the second cell layer92 respectively, on a glass substrate of dimensions 1.4 m×1.1 m.Subsequently, the substrate was divided in two, forming tandem-typesolar cell modules of dimensions 0.7 m×1.1 m. Deposition of thecrystalline silicon i-layer 42 was conducted at a deposition rate of 2nm/sec, and the applied electric power and the hydrogen dilution ratiowere adjusted appropriately to control the crystallinity distributionwithin the substrate plane.

Following measurement of the solar cell module output, the substrate waspartitioned. The Raman spectrum was measured for samples taken from 24locations within the substrate plane, and the crystallinity 1c/1a wasdetermined. Prior to measurement of the Raman spectrum, the backelectrode layer 4 was removed from each sample using hydrogen peroxide(concentration: 30%) and dilute hydrochloric acid (molar concentration:0.2), so that the crystalline silicon n-layer 43 was exposed at thesurface.

The output of the produced solar cell module, the distribution range,average value, and standard deviation for the Raman peak ratio for thecrystalline silicon i-layer, and the proportion of regions having aRaman peak ratio of not more than 4 are shown in Table 2. The standarddeviation was not less than 1 and not more than 3 for all of thesamples. The film thickness distribution for the crystalline siliconi-layer was within a range from ±15 to 25% relative to the average filmthickness.

TABLE 2 Proportion of regions having Raman Module Raman peak AverageStandard peak ratio of not output ratio range value deviation more than4 (%) (W) 4~7 5.5 1.2 1 80 4~8 6 1.3 0 78 5~9 7 1.3 0 76 4~6 5 1.0 3 843~8 5.5 1.4 8 78 3~7 5 1.3 10 78 3~6 4.5 1.2 15 74 3~6 3.8 1.1 20 58 2~63.8 1.2 30 55 2~6 3.3 1.1 55 37

FIG. 9 illustrates the relationship between the average value for theRaman peak ratio and the solar cell module output. In this figure, thehorizontal axis represents the average value for the Raman peak ratio,and the vertical axis represents the module output. A high output wasobtained for those solar cell modules having an average value of notless than 4 and not more than 8. FIG. 10 illustrates the relationshipbetween the proportion of regions having a Raman peak ratio of not morethan 4 and the solar cell module output. In this figure, the horizontalaxis represents the proportion of regions having a Raman peak ratio ofnot more than 4, and the vertical axis represents the module output. Ahigh output was obtained for proportions of 15% or less. In contrast,once this proportion exceeded 15%, the output exhibited a decliningtrend. Further, peeling of the crystalline silicon i-layer was alsoobserved.

As described above, for a solar cell module having a crystalline siliconi-layer for which the Raman peak ratio within the substrate plane had anaverage value of not less than 4 and not more than 8 and a standarddeviation of not less than 1 and not more than 3, and for which theproportion of regions having a Raman peak ratio of not more than 4 wasnot more than 15%, a high output equivalent to at least 88% of themaximum initial output (84 W) was obtained.

Example 3

Using a CVD method, a first cell layer 91 comprising an amorphoussilicon i-layer having a film thickness of 220 nm or 350 nm was formedon a glass substrate of dimensions 1.4 m×1.1 m. In order not to alterthe productivity of the solar cell module, the deposition process wasadjusted so that the amorphous silicon i-layers were deposited over thesame deposition time. A CVD method was then used to form, on top of thefirst cell layer 91, a second cell layer 92 having a crystalline siliconi-layer of Example 1, for which the Raman peak ratio exhibited a rangefrom 3 to 10, an average value of 6.3 and a standard deviation of 1.7,and for which the proportion of regions having a Raman peak ratio of notmore than 4 was 3% or less, thus completing a tandem-type solar cellmodule.

Table 3 shows the average film thickness of the amorphous siliconi-layer within the solar cell module, the average film thickness of thecrystalline silicon i-layer, and the stabilized output for the solarcell module 1,000 hours after starting electric power generation. Thefilm thickness distributions for the amorphous silicon i-layer and thecrystalline silicon i-layer were each within a range from ±15 to 25%relative to the average film thickness.

TABLE 3 Average film Average film thickness of thickness of amorphoussilicon crystalline silicon Stabilized i-layer (nm) i-layer (nm) output(W) 220 2100 150 350 2100 137

As shown in Table 3, by adopting a thin amorphous silicon i-layer havinga film thickness of 220 nm, light-induced degradation was controlled,and the stabilized output was able to be increased.

Example 4

A solar cell module comprising an intermediate contact layer 5 having anaverage film thickness of 50 nm, and a solar cell module having nointermediate contact layer were prepared (each using a substrate ofdimensions 1.4 m×1.1 m). In the solar cell module comprising theintermediate contact layer, the film thickness of the amorphous siliconi-layer of the first cell layer 91 was set to 220 nm. In the solar cellmodule having no intermediate contact layer, the film thickness of theamorphous silicon i-layer was set to 320 nm in order to achieve electricpower generation current consistency between the first cell layer andthe second cell layer. Moreover, in order not to alter the productivity,the deposition process was adjusted so that the amorphous siliconi-layers were deposited over the same deposition time. In each of thesolar cell modules, the second cell layer 92 was formed so that thecrystalline silicon i-layer exhibited a Raman peak ratio having a rangefrom 3 to 10, an average value of 6.3 and a standard deviation of 1.7,and had a proportion of regions having a Raman peak ratio of not morethan 4 that was 3% or less.

Table 4 shows the average film thickness of the intermediate contactlayer of the solar cell module, the average film thickness of theamorphous silicon i-layer, the average film thickness of the crystallinesilicon i-layer, and the stabilized output for the solar cell module1,000 hours after starting electric power generation. The film thicknessdistributions for the amorphous silicon i-layer and the crystallinesilicon i-layer were each within a range from ±15 to 25% relative to theaverage film thickness.

TABLE 4 Average film Average film Average film thickness of thickness ofthickness of intermediate amorphous silicon crystalline siliconStabilized contact layer (nm) i-layer (nm) i-layer (nm) output (W) 50 nm220 2100 150 None 320 2100 131

As shown in Table 4, by providing an intermediate contact layer, thefilm thickness of the amorphous silicon i-layer was able to be reduced.As a result, light-induced degradation was controlled, and thestabilized output was able to be increased.

It should be noted that the present invention is in no way limited bythe embodiments described above, and various combinations are possiblewithin the scope of the present.

The invention claimed is:
 1. A photovoltaic device comprising: asubstrate; and a photovoltaic layer comprising a crystalline siliconlayer formed on the substrate, wherein the crystalline silicon layer hasa crystalline silicon i-layer, and the crystalline silicon i-layer has asubstrate in-plane distribution represented by an average value for aRaman peak ratio, which represents a ratio of a Raman peak intensity fora crystalline silicon phase relative to a Raman peak intensity for anamorphous silicon phase, wherein the Raman peak ratio is not less than 4and not more than 8, a standard deviation for the Raman peak ratio thatis not less than 1 and not more than 3, and a proportion of regions, notless than 1% and not more than 3%, in which the Raman peak ratio is notmore than
 4. 2. The photovoltaic device according to claim 1, whereinthe crystalline silicon i-layer is deposited at a deposition rate of notless than 1.5 nm/sec.
 3. The photovoltaic device according to claim 2,wherein the photovoltaic layer further comprises an amorphous siliconlayer including an amorphous silicon i-layer, and a film thickness ofthe amorphous silicon i-layer within said amorphous silicon layer is notless than 170 nm and not more than 250 nm.
 4. The photovoltaic deviceaccording to claim 3, further comprising an intermediate contact layerbetween the crystalline silicon layer and the amorphous silicon layer.5. The photovoltaic device according to claim 1, wherein thephotovoltaic layer further comprises an amorphous silicon layerincluding an amorphous silicon i-layer, and a film thickness of theamorphous silicon i-layer within said amorphous silicon layer is notless than 170 nm and not more than 250 nm.
 6. The photovoltaic deviceaccording to claim 5, further comprising an intermediate contact layerbetween the crystalline silicon layer and the amorphous silicon layer.7. A photovoltaic device comprising: a substrate; and a photovoltaiclayer comprising a crystalline silicon layer formed on the substrate,wherein the crystalline silicon layer has a crystalline silicon i-layer,a size of a surface of the substrate on which the photovoltaic layer isformed is at least 1 m square, and the crystalline silicon i-layer has asubstrate in-plane distribution represented by an average value for aRaman peak ratio, which represents a ratio of a Raman peak intensity fora crystalline silicon phase relative to a Raman peak intensity for anamorphous silicon phase, wherein the Raman peak ratio is not less than 5and not more than 8, a standard deviation for the Raman peak ratio thatis not less than 1 and not more than 3, and a proportion of regions, notless than 2% and not more than 6%, in which the Raman peak ratio is notmore than
 4. 8. The photovoltaic device according to claim 7, whereinthe crystalline silicon i-layer is deposited at a deposition rate of notless than 1.5 nm/sec.
 9. The photovoltaic device according to claim 8,wherein the photovoltaic layer further comprises an amorphous siliconlayer including an amorphous silicon i-layer, and a film thickness ofthe amorphous silicon i-layer within said amorphous silicon layer is notless than 170 nm and not more than 250 nm.
 10. The photovoltaic deviceaccording to claim 9, further comprising an intermediate contact layerbetween the crystalline silicon layer and the amorphous silicon layer.11. The photovoltaic device according to claim 7, wherein thephotovoltaic layer further comprises an amorphous silicon layerincluding an amorphous silicon i-layer, and a film thickness of theamorphous silicon i-layer within said amorphous silicon layer is notless than 170 nm and not more than 250 nm.
 12. The photovoltaic deviceaccording to claim 11, further comprising an intermediate contact layerbetween the crystalline silicon layer and the amorphous silicon layer.